Reinforcing fitting for deck openings



Nov. 2, 1943. H. B, MARIS ETAL REINFORCING FITTING FOR DECK OPENINGS Filed Dec. 3, 1942 v ELEE=3 Patented Nov. 2, 1943 REINFORCING FITTING FOR DECK I OPENINGS 7 Harry BJMaris and John A. Sanderson, Washington, 0.

Application December 3, 1942. Serial No. 467,738 H (Granted under the act of March 3, 1883, as l a amended April 30, 1928; 370 0. G.;757)- 7 Claims.

1 This invention relates toa reinforcing fitting for use around hatch and other openings in decks or similar structures.

g It is well known that high concentrations of stress occur in the deck plates of ships around the corners of openings of a rectangular or similar shape when the deck is placed under tension. The application of such stresses to the decks of ships is a matter of common occurrence, since it takes place each time the ship is supported by a wave or swell beneath its mid-section while its'ends are lying in the troughs of such waves.

For this reason, such openings, though neces sary, constitute a serious impairment of the strength and seaworthiness of the vessel. 7 In the past it has been common practice to double the thickness of the deck plating around the edges of such openings in an effort to overcome the above mentioned weakening eifect. While this practice usually succeeded in protecting the plating around the edge of the opening, in doing so it often introduced high concentrations of stress in the plating at other points. It is an object of this inventionto provide, a reinforcing'means for use around rectangular and other openings in decks or, similar structures which, when the; deck is under tension, will prevent the formation of high concentrations of stress due to the presence of the opening.

It is a further object of theinvention to provide reinforcing means around such openings to take. the load which would have been borne bythe omitted plating, said reinforcing means being of such construction and form that its behavior with respect to the surrounding plate, while undergoing such stress; will be substantially that of the omitted plate. 1- 7 Other objects will become apparent from a careful consideration of the following description when taken together with the accompanying' drawing in which: i t

Fig. 1' is a plan view of a segment of deck plating having a rectangular opening formed therein and a reinforcing means embodying the invention applied thereto; v

Fig. 2 is a cross-sectional view taken alon the line 22 of Fig. 1, and:

Fig. 3 Ba plan view-of a second embodiment of the invention.

In Fig. 1 there is represented by reference character ID a section of a deck of a ship, the stress in the deck being a uniform tension along the Y axis as shown by the arrows. "The deck has fo'rmedin it a rectangularopening H such as'might constitute a part of a hatch.

In accordancewith the invention, accumulations of stress are'preventedby the use of a re-' inforcing fitting employing the principles of the 1 suspension bridge. -Such a fitting is-indicated generally inFig. l by the reference numeral [2.

It is made up of a plurality of connected members, two of which marked AB and CD, extend parallel to opposite sides of opening H and likewise parallel to the direction of the lines of stress. A and C are members BND and AOC'respectively, both formed in the shape of substantially Parabolic arches 1 These arches receive the load from the deck plating and transmit it to the longitudinalmembers AB and CD; Transversemernbers AC and BD are provided at'the bases or the arches to withstand compressional stresses along the axis and thus serve to maintain equilibrium between the forces in AOC and BND and th forces in AB and CD It,wil1 be seen that the arches of the fitting act in the same capacity as the cables of a suspension bridge, the road bed of which is of uniform weight per unit length. The uniform tension existing in. theplating and represented by the arrows in Fig. 1 corresponds to the weight of the road bed of the suspension bridge.

It will be noted that in Figure 2 the fitting is shown as made of I-beams. This, however, is only'byway of example, as the fittingmay equally well be .made up of sheet stock. If important bending stresses in the beam resulting from the non-symmetrical load applied only to one side are tobe avoided, the height of the stock or beam section above the plating should be less \than th of the overall length of the fitting. The fitting may be cast as a whole or may be fabricated, various parts being joined bytany convenientmeans such as welding or riveting. The fitting is shown at 3 in this figure .as being joined to the deck plating by welding. Any other convenient means of securing it to the deck maybe followed. However, regardless of what method is employed, the points of connection between the fitting and the deck'plating should be numerous and equally spaced; Although the fitting is shown in Figures 1 and 2 asbeing applied to the upper surface of 'the deck plating, it may be applied to the lower surface if desired.

The cross-sectional area of each fitting member should be equal to the product ofthe half- Connecting points B and D an'd'points the allowable dimensions and weight of the fitting. It has .been found that tangent, :2.5

represents a practical value resulting in a fitting in the form of Figure 1.

With the type of fitting illustrated'in Figure. 1, concentrations of stress in the plate are. only 6% greater than the applied. tensile. stren th, whereas if no fittingis used, concentrationsof stress as much as 100% greater than the applied tensile strength may be expected.

The efiiciency of any fitting ordiffer ntshape will be less than that of the parabolic form here described-butwi-ll efiicient in proportion to. its approximation to the paraboliciQr-m, In Fig. 3 is shown a fittiugsimilar to that of Fig. 1 but havingits arches-composed, 0f ohqrdsl ske meme bars which-approximate .the parabolic curv 3. Means for reenforcing the edges of an opening in a plate which is under uniform unidirectional tension, comprising a fitting secured to said plate around said opening, said fitting comprising a pair of longitudinal members extending along opposite sides of said opening and parallel to the direction of application of said tension, a pair of members, each having substantially the Shape of a parabola and each joining a pair of corresponding ends of said longitudinal members,

' and a transverse member extending between the ends of'each of said parabolic members, all of said members being rigidly secured together into Thuspoints Band D are'joinedi by chords-BS,

ST and TD and the points Aand Care joined by chords- ;AQ, QR and no.1; Such a fitt ns'has been found toqolosely approach theihehavior of, the ideal type shown in Fig. 1.

While the use of'thefittings embodying the invention has been; shown only as applied to rectangumr" deckopenin s, they may l kew s be applied;toopenirigsof other shap s. If the opening does not have sides parallel to the direction of applicationof stress, than the crosssectional area of the, membersz shouldbe calculatedby substituting half the maximum dimen sionttransverseltolongitudinal members AB and CDfor-thehalf-width of the opening.

The invention described herein may be man'ue factured and used by prior the Government of the United States of America for governmental purposes without the paymentof-any royalties thereon or therefor. I I

We claim: r r r 1. Means for reenforcingthe edges ofan open ingfi'n a plate which is under uniform unidirectional tension, comprising a fitting secured to said plate around said opening'said fitting comprising a pair of longitudinal members extending along opposite sides'of saidopening and parallel to thedirection'of application of said tension, pair of members extending transvers ely'between said longitudinalmembers, and a pair of ,members each having substantially the form of'a parabolaand each joining a pair of corresponding ends of saidlongitudinal members, all of said. members being rigidly secured together intofa' unitary structure. n

2'. Means for reenforcing the edges of an open: ing in a plate which is under uniform n directional tension, comprising a. fitting secured to said platearound said opening, said fitting comprising a pair or longitudinal'members exten in along opposite sidesoffsaid opening and parallel to the direction of application of saidtension, a pair of members. each having substantially. the

shape of a parabola andeachjoining a pail of M p nding e ds of said longitudinal member and atransverse memberextending between the ends of each of said parabolic members, all of said members being rigidly secured together into aunitary structure. I i g V a unitary structure, the cross-sectional area of said longitudinal and parabolic members being equal to the product of half the maximum di. mension of said opening in a direction transverse to said longitudinal members and the thickness of said plate.

4. Means for reenforcing the edges of an opening in a platewhich is under uniform unidirectional tension, comprising a fitting secured to said plate around said opening, said fitting com.- prising a pair, of longitudinal members extending along opposite sides ofsaid opening and parallel to the direction of application of said tension, a pair of members, each having substantially the shape of a parabola and .each joining a pair of corresponding ends of said longitudinal members, and a transverse member extending between the ends of each of said parabolic members, all of said members being rigidly secured together intoa unitary structure, the cross-sectional area of said longitudinal and parabolic members being equal to the product of half the maximum dimension of said opening in a direction transverse to said longitudinal members andthe thickness of said plate, and the compressional strength of each of said transverse members being equal to the product of the maxi.-

.mum expected stress on one of said longitudinal members and the co-tangent of the angle betwe n. a l n tan en o one, of said pa abolic memb r at ts point of ori in nd a l ne o mal t he directi n of. app i ation of sai st e s.

5. M ns for re ni 'r ins he ed e o an openns in a p at wh ch s und r un i munidireetion tens on, comprisin 'a'fittin secure to said plate around said opening, said fitting coma prising a pair of longitudinal members extending along opposite sides of said 7 opening and parallelto the direction of application of said tension, a pair of members, each composed. of at least three segments symmetrically proportioned and forming chords of a parabola, each of said members joining a pair of corresponding ends of said longitudinal members, and a'transverse member extending between the ends of said longitudinal members, all of said members being rigidly secured together into a unitary structure.

6. Means for reenforcing the edges of anopening in a plate which is under unifor'rnunidirectional tension, comprising a'fittiri'g secured to said plate around said opening, said fitting comprising a pair of longitudinal members extending along opposite sides of said opening and parallel to the direction of application of said tension, a pair of members, each composed of at least. three segments symmetrically; proportioned and. form-: i g ch ds of a par b la. .eaeh'of sa d members joining a pair of corresponding endsjoj longi-. tud al m e and a, a s erse in 3' extending between the ends of said lo gitudinal members, all of. said .members; being rigidly cured together into a unitary structure, the cross;

sectional area of said longitudinal and segmented members being equal to the product of half the maximum dimension of said opening in a direction transverse to said longitudinal members and the thickness of said plate.

'7. Means for reenforcing the edges of an opening in a plate which is under uniform unidirectional tension, comprising a fitting secured to said plate around said opening, said fitting comprising .a pair of longitudinal members extending 10 along opposite sides of said opening and parallel to the direction of application of said tension, a

pair of members, each composed of a plurality of segments symmetrically proportioned and forming chords of a parabola, each of said members joining a pair of corresponding ends of said longitudinal members, and a transverse member extending between the ends of said longitudinal members, all of said members being rigidly secured together into a unitary structure.

HARRY B. MARIS.

JOHN A. vSANDERSON. 

